A Raspberry Pi Keyboard Latency Tester GPIO18

rpi_keyboard_latency_tester.py

###
# Portland.HODL USB HID Latency Tester
# Engineered for RaspberryPi(4/5)

import csv
import hid
import time
import RPi.GPIO as GPIO

def list_hid_devices():
    devices = hid.enumerate()
    return devices

def display_devices(devices):
    print("Available HID Devices:")
    for idx, device in enumerate(devices):
        vid_hex = hex(device['vendor_id'])
        pid_hex = hex(device['product_id'])
        print(f"{idx + 1}. Vendor ID: {vid_hex}, Product ID: {pid_hex}")

def select_device(devices):
    while True:
        choice = input("Start a test on (number): ")
        if choice.isdigit() and 1 <= int(choice) <= len(devices):
            return devices[int(choice) - 1]
        else:
            print("Invalid selection. Please try again.")

def main():
    GPIO.setmode(GPIO.BCM)  # or GPIO.setmode(GPIO.BOARD)
    GPIO.setup(18, GPIO.OUT)  # Set pin 18 as an output pin
    GPIO.output(18, GPIO.HIGH)  # Turn on the LED

    # Lets setup the GPIO pins
    devices = list_hid_devices()
    display_devices(devices)
    selected_device = select_device(devices)

    # Now lets Open the selected HID device
    try:
        keyboard = hid.device()
        keyboard.open(selected_device['vendor_id'], selected_device['product_id'])  # open device
        print("Device opened successfully")
        test_cnt = 0
        test_results = []
        start_times = []
        final_times = []

        while test_cnt < 1000000:
            time_ns_start = time.perf_counter_ns()
            GPIO.output(18, GPIO.LOW)  # Press the active low key
            start_times.append(time_ns_start)  # Store start time
            data = []
            data = keyboard.read(8)
            final_time = time.perf_counter_ns() - time_ns_start
            final_times.append(final_time)
            GPIO.output(18, GPIO.HIGH)  # Release the active low k[]ey
            test_results.append((time_ns_start, final_time))  # Store start time and total time
            test_cnt += 1
            data = keyboard.read(8)

        # Filter and prepare data for CSV
        filtered_data_for_csv = [(start, total) for start, total in test_results if total <= 100000000]
        print(f'Average time of {(sum(final_times) / len(final_times)) / 1000000000 * 1000}ms')

        # Write to CSV
        with open('latency_results.csv', 'w', newline='') as csvfile:
            writer = csv.writer(csvfile)
            writer.writerow(['Start Time', 'Total Time'])  # Header
            for result in filtered_data_for_csv:
                writer.writerow(result)

        print("Results written to test_results.csv")
    except IOError as e:
        print(f"Error opening device: {e}")
    finally:
        GPIO.cleanup()
        keyboard.close()
        print("Device closed")

if __name__ == "__main__":
    main()